1. Field of the Invention
The present invention relates to a rotary nozzle system which is attached to the bottom outlet of a metallurgical vessel, such as, a ladle or tundish, whereby its slide plate brick is rotated so as to adjust the opening and closing or the degree of opening of a nozzle bore formed in a fixed bottom plate brick and thereby to control the rate of pouring of molten steel or the like.
2. Description of the Prior Art
Rotary nozzle systems have been used widely with ladles for receiving the molten steel tapped from a converter to transport or pour the molten steel into molds, tundishes for receiving the molten steel from a ladle to pour the molten steel into molds and the like.
A good example of this type of rotary nozzle system is shown in U.S. Pat. No. 4,591,080.
The conventional rotary nozzle system is disadvantageous in that there is the danger of the slag or the like entering between the sliding surfaces of the slide plate brick and the fixed bottom plate brick and causing leakage of the molten steel. The entry of the slag or the like between the sliding surfaces is promoted by the occurrence of cracks extending radially from the nozzle bores in the fixed and slide plate bricks and therefore it is necessary to bind each of the plate bricks all around its periphery from outside with a steel band or the like. Also, during the closing of the nozzle bores, if the interfacial pressure between the brick sliding surfaces which varies in inverse proportion to the magnitude of the area of contact between the plate bricks is allowed to rise slowly, the force of the molten steel flowing through the throttled flow passage acts in directions tending to separate the sliding surfaces from each other and thus the molten steel tends to enter between the sliding surfaces. Moreover, there are cases where the fixed bottom plate brick shifts during the rotation of the slide plate brick and such movement causes an excessive sliding movement, thereby promoting the entry of the molten steel between the sliding surfaces.